Heat exchange unit



2 Sheets-Sheet 1 HEAT EXCHANGE UNIT Filed Sept.- 11, 1939 W. E2MCULLOUGH ETAL March 31, 1942.

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March 31, 1942. w MCCULLOUGH ET AL 2,277,921

HEAT EXCHANGE UNIT Filed Sept. 11, 1939 2 Sheets-Sheet 2 L Y%/:;Z/77E/VcCu//0u 5% ATTORNE Patented Mar. 31, 1942 I William E.McCullough and Allen L. Goldsmith,

.Detroit, Mich., assignors to Bohn Aluminum & Brass Corporation,Detroit, Mich., a corpo- Q ration of Michigan 1 Application September11, 1939 Serial No. 294,310 7 2 Claims. (011257-150) This inventionrelatesto a heat exchange unit of the coiled type. A principal'object ofthe in-' vention is the provision of a heat'exchange unit formed of astrip of extruded metal, such as aluminum, in which lateral fins are'formed homogeneous with the tubing of the heat exchange strip.' Thestrip is coiled sothat the finished unit has a substantially circularshape corresponding to the air stream from -a fan, and the laterallyextending fins are deformed so as spirally with-adjacent convolutionsspaced from 1 each other as shown in Fig. '2. v The-fins =1 l which faceto the front in Fig. -1' are" then bent out-- wardly so that eachannulus of the fin N forms a substantially funnel-shapedfmeinb er. Thefins l2 on the opposite side of the strip are coned in the oppositedirection so as to form a continuation of the funnel'shape on -theopposite side of the tubular section ill.

to project into-the space between adjacent runs of the strip to increasethe efficiency of heat transfer between the moving air column and theheat exchange unit.

In one form of the invention the fins are bent so as to form a series offunnel-shaped rings, and in another form the outer edges of the fins arefluted, both of these constructions serving as inclined surfaces uponwhich the air stream impinges.

While preferred forms of the device are disclosed. herein for purposesof illustration, it should be understood that various changes may bemade in the structure and arrangement of parts without departing fromthe spirit of the invention as herein set forth and claimed.

In the drawings:

The heat exchange unit thus formed, which is particularly useful asacondenser for mechanical refrigeration'systems", may be provided withFig. l is a side elevation of a heat exchange unit made according to thepresent invention.

Fig. 2 is a section on line 2-2 of Fig. 1.

Fig.3 is a fragmentary section of the device of Fig. 1. s

Fig. 4 is a perspective view of a fragment of extruded strip of modifiedform.

Fig. 5 is a view similar to Fig. 4 showing another form.

Fig. 6 is a view similar to Fig. 1 but showing another arrangement ofthe fins.

Fig. 'l is a view similar to Fig. 6 illustrating an additionalmodification.

Fig. 8 is a section taken on line a-8 of Fig. 6..

Referring 'to the drawings more particularly,

Figs. 1 and 2 illustrate aform of the invention in which the'unit ismade from an extruded strip which, as originally extruded, consists of acylindrical tubular section It! from which fins ii and I2 extend in,opposite directions and parallel to each other. A piece of this extrudedstrip of length sufiicient to give thedesired'heat exchange capacity isthen prepared by removing the'fins II and I2 from the ends of the stripso as to expose-the tubular part It), and these ends are suitablyprepared for connection to other conduits as by having the flare tubecouplings tfiiriountedthereon. .The strip is then wound any suitablemeans for mounting it in the vertical position illustrated in Fig; 1.The means illustrated consists ofa strap 14 having a T- shapedcross-section including a head l5 and a leg l6. Part of the leg I6 isremoved at an intermediate part of the strap M for a distancecorresponding to the thickness of the coil of extruded strip. The strap14 is then bent into substantially U-shape as illustrated in Fig. 3. Agroove corresponding to the size of the leg I6 is milled straight acrossthe coil on both sides, and the bent strap I4 is then assembled over thecoil by sliding the legs [6 into the slots formed in the fins II and I2as illustrated in Fig. 3. The strap I4 is attached to the fins ll and I!in any suitable manner as by oven brazing. This latter process isparticularly advantageous in this connection because each individualcoil of the strip is thereby rigidly connected to both parts of thestrap Id. The lower ends of the strap l8 are formed in any suitable wayfor mounting on a base as, for example, by bending the ends outwardly toform feet 11 which may be suitably braced and mounted on a support.

The heat exchange unit is preferably mounted with a. fan directing anair stream against the front face of the coil as shown in Fig. 1. Theair stream from the fan thus strikes against the cone-shaped fins H,wipes around the cylindrical tube l0, and then impinges upon thecone-shaped fins l2'before emerging from the heat exchange unit. Thisarrangement provides for a positive wiping action of the air across thefins H and I2 as well as around'the tubular section II), thus inducingemcient heat exchange between the air and the unit.

In the form just described the central tubular portion was madecylindrical because that section is best adapted" to installations wherea fluid passing through the tube is under a relatively high pressure.However, it will be understood strip l8 illustrated in Fig. 4 has asubstantially oval tubular section. and in the strip 18 illustrated inFig. 5, the central section has an angular outer periphery pierced by acylindrical tubular opening. The strip may or course be extruded fromother suitable materials, but aluminum is at present the preferredmaterial.

It is particularly advantageous to have the lateral fins bent so as toextend beyond the lateral boundaries of the central tubular section soas to increase the area of the heat exchange unit upon which the airstream impinges. This object was accomplished in the form of Figs. 1 and2 by bending the fins into coned or funnel shape. This result can, ofcourse, be obtained by other arrangements. For example, in the formillustrated in Fig. 6 the lateral flanges the extruded strip are ruilledor fluted so that while the part of each fin adjacent the tube I0 formsa straight line, its outer end is fluted or ruiiied with the crests 20of the flutes extending beyond the lateral boundaries of the tubesection In. In manufacturing this form of the invention the ruflles orflutes are preferably rolled into the fins while the strip is in fiatcondition so that when the strip is coiled into the shape illustrated inFig. 6, the crests of the flutes are in hit or miss" relation to eachother.

On the other hand, in the modification illustrated in Figs. 7 and 8 theflutes are pressed into the fins by fixtures after the strip has beencoiled, and the crests of one turn of the coil are arranged in radialalignment with the crests of the turn beyond. In this way the ruiliesform a series oi Venturi openings which narrow down toward the tubeparts It), and then expand again on the back side of the unit. Theadvantages of these Venturi openings in increasing the velocity 01' airflow over the tubes In is well known in the art. In order to have thisorderly arrangement of the crests 20, it is necessary to form theruflles of increasing length going from the center turn of the coiltoward the periphery so that entrances to the Venturi throats are largerin the outer turns than they are in the inner turns.

The arrangement in which the ruiiles of ad- {lacent runs of tubing arealined to provide enturi openings is claimed in co-pending applicationSerial No. 279,617, filed June 17, 1939 by William E. McCullough.

We claim:

1. A heat exchange unit comprising a single legnth or stock having atube section and homogeneous fins, a fin extending laterally from eachside of the tube section, the strip being formed into a coil withadjacent turns spaced apart so as to provide space for air streams, atleast one of the lateral fins being deformed into a substantiallyconical rim extending from the tube section.

2'. A heat exchange unit comprising a single length of stock having atube section and homogeneous fins, a fin extending laterally from eachside of the tube section, the strip being formed into a coil withadjacent turns spaced apart so as to provide space for air streams, bothlateral fins being bent so as to form substantially funnel-shapedopenings through the unit.

ALLEN L. GOLDSMITH. WILLIAM E. McCULLOUGH.

